When replacing a diverter valve in your hot tub, the biggest mistake people make is misunderstanding the size.
Let’s clear that up right now.
What “1-Inch” and “2-Inch” Actually Mean
The size of a diverter valve does NOT refer to:
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The size of the cap
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The diameter of the handle
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The outside measurement of the top
It refers strictly to the plumbing that glues into the valve body.
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A 1-inch diverter accepts 1-inch plumbing
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A 2-inch diverter accepts 2-inch plumbing
That’s the determining factor.
Measuring the Threads (This Is What Matters)
If you measure across the threaded portion of the cap:
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A 1-inch valve will measure roughly 1 5/8" across the threads
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A 2-inch valve will measure approximately 2 3/4" across the threads
Now here’s where it gets confusing:
The outer cap width on 2-inch models may range from 3 1/4" all the way to 5" depending on style.
But the thread diameter is what determines compatibility.
Always match thread width first.
What Does a Diverter Valve Do?
A diverter valve redirects water pressure inside your spa.
Common uses:
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1-inch valves → neck jets, small jet groups, waterfalls
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2-inch valves → foot jets, large jet clusters, multi-zone control
Turn it left for one jet group.
Turn it right for another.
Center position activates both.
It increases jet pressure by focusing water where you want it.
Major Manufacturers & Interchangeability
Most diverter designs trace back to:
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HydroAir
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Waterway Plastics
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CMP
Waterway and CMP models are largely interchangeable with HydroAir-style designs as long as thread dimensions match.
Some spa brands customize the appearance but use the same internal design.
For example:
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Cal Spas
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Dynasty Spas
They may look different cosmetically, but many will interchange mechanically.
Buttress vs Standard Threads (2-Inch Valves)
On 2-inch diverters you may encounter:
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Buttress thread design
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Standard (non-buttress) threads
In most cases they will swap out without issue.
However:
If your cap says “Buttress” underneath — stick with buttress.
If it does not, standard threads are typically correct.
Common Failure Points
Over time, diverter assemblies can fail due to:
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Cracked threads
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Broken caps
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Worn or flattened O-rings
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Valve body sagging under the shell
As hot tubs age, the plumbing becomes rigid. The shell may flex slightly. When that happens, the diverter body can pull downward.
This causes:
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Reduced visible thread length
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Caps that won’t tighten
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Caps that pop off
In severe cases, the cabinet must be opened and the valve repositioned or replaced entirely.
Can You Upgrade the Style?
Yes.
You are not locked into the original appearance.
Modern six-spoke caps, larger grip handles, and updated finishes can often be installed as long as:
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Thread diameter matches
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Plumbing size matches
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Buttress type matches (if applicable)
Just verify clearance if upgrading to larger 2-inch caps — some are nearly 5" across.
Special Note on Premium Models
Some manufacturers, such as Jacuzzi, use diverters that measure around 3 7/8" across the threads.
They function similarly to 2-inch valves but use proprietary sizing.
Always measure before ordering.
How SpaPartsNet Makes It Easy
At SpaPartsNet.com you can search by:
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1-inch diverter valves
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2-inch diverter valves
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Brand compatibility
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Color
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Cap style
Not sure what you need?
Text us photos.
Send clear pictures of:
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The top of the cap
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The threads
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The plumbing underneath (if possible)
Tell us if you want to replace or upgrade.
We’ll send direct links so you get the right part the first time.
Ordering incorrectly wastes time and money — and we work hard to prevent that.
This is The Hot Tub Professor.
More technical breakdowns coming soon.
Visit us at:
SpaPartsNet.com